Indications on the ND

If the PFD answers "what is my attitude and speed", the ND answers "where am I, what is around me, where am I going" — the medium-term situation screen. As with the PFD, where the navaids come from, how the flight plan is computed, how the weather radar scans belong to ATA-34/22; ATA-31 owns how this screen presents them: six modes, a colour language (which line is what colour, which navaid is what colour), two overlayable layers (weather, terrain), and the centre messages and flags when data fails.

1. Six modes — five navigation, one engine standby

Per FCOM DSC-31-45:

"There are six different displays (five display navigation information, and one displays primary engine parameters): - ROSE LS - ROSE VOR - ROSE NAV - ARC - PLAN - ENG (standby page). The Navigation Display (ND) can provide a weather radar image in all modes, except PLAN."

Two points: (1) five navigation modes plus one ENG standby page — ENG puts the E/WD engine parameters on the ND, a backup for a failed E/WD; (2) only PLAN cannot overlay the weather radar (PLAN is a true-north static plan, not rotating with the aircraft, so radar is meaningless). ARC and ROSE NAV carry the same information, differing only in extent. Per FCOM DSC-31-45:

"ROSE NAV and ARC modes provide the same information to the flight crew, but ARC mode limits it to the forward 90 ° sector."

ARC = the forward-90° version of ROSE NAV — sacrificing the sides and rear for a larger forward scale. ARC is common in cruise (see far ahead) and on approach.

2. Permanent data — wind, ground speed, true airspeed, bearing pointers

Whatever the NAV mode, the ND shows a base set of data. Per FCOM DSC-31-45:

"...direction is given relative to True North. The ND displays a green arrow when one of the following conditions occur: - Wind speed exceeds 2 kt, or - TAS is above 100 kt. The green arrow indicates the wind direction relative to Magnetic North. When wind data is not received... dashes replace the numbers."

A counter-intuitive point worth flagging: the wind direction figure is relative to true north, but the green arrow is relative to magnetic north — the number and the arrow use different reference norths. The figure follows the meteorological convention (true), the arrow the pilot's instinct (wind relative to current magnetic heading). Ground speed and true airspeed come from the ADIRS; VOR/ADF bearing pointers hang per the EFIS CP ADF-VOR selector; the chronometer shows per the glareshield CHRONO button (see the electrical clock).

3. The flight-plan lines — five lines, five colours

The ND distinguishes flight-plan nature by colour, a code to memorise. Per FCOM DSC-31-45:

"- The active flight plan... is indicated by a continuous green line... - Missed approach procedure... indicated by a continuous blue line. - Alternate... indicated by a dashed blue line. - The secondary flight plan... indicated by a continuous white line. - Temporary flight plan... indicated by a dotted yellow line."

The mnemonic: active green, missed-approach blue, alternate dashed blue, secondary white, temporary dotted yellow. The logic is easy — green = what you are flying, blue = a plan (missed-approach solid / alternate dashed), white = a stored second plan, dotted yellow = an unconfirmed temporary revision (yellow always means "not active / pending", consistent with the other yellow-dashed items on the PFD/ND). An invalid active plan is shown dashed green. The ND shows only the flight plan ahead of the aircraft (FMS computation in ATA-22).

4. Navaid symbols — four shapes × four colours

Navaid symbols use shape for "which kind of station" and colour for "what relation to the flight plan". First the shapes. Per FCOM DSC-31-45:

"NAVAIDS. The display uses all of the following specific symbols for NAVAIDs: DME or TACAN; VOR; VOR/DME; NDB."

Four kinds, four symbol shapes (DME/TACAN, VOR, VOR/DME, NDB each with a distinct figure) — the shape tells you what facility it is. Overlay colour for its flight-plan relation. Per FCOM DSC-31-45:

"The symbol can appear in all of the four following colors: - In green if the NAVAID is a current waypoint of the flight plan - In white if it is the TO waypoint - In blue when the NAVAID is tuned for display, either automatically by the FMGEC, or manually via the MCDU - In magenta when the NAVAID is not part of the flight plan and is displayed as an option."

Four colours: green = a current flight-plan waypoint, white = the TO (next) waypoint, blue = tuned for display, magenta = not in the plan, displayed as an option (the corresponding EFIS CP button pressed). The anchor, consistent with the PFD, is "white = TO, magenta = optional/extra". With shape and colour understood, the ND ceases to be a scatter of points and becomes "who is in the plan, who is next, who I chose to look at".

5. Crosstrack error — how many miles off, which side

Per FCOM DSC-31-45:

"This is the lateral deviation of the aircraft from the active leg of the flight plan (related to the great circle route). It is indicated in nautical miles (NM), with the letter R (right) or L (left), according to the position of the aircraft compared to the flight plan... The cross-track error is displayed with a precision of two digits (0.01 NM), from 0.02 NM to 0.29 NM."

Crosstrack-error resolution tightens with navigation accuracy — two digits (0.01 NM) at high accuracy (RNP ≤ 0.3 context), one digit (0.1 NM) when coarser, cleared below 0.01 NM — so precise navigation shows the smallest deviation. This binds to RNP AR operation (ATA-34) and is the display-side basis for the MEL clause "one PFD/ND failed → no RNP AR" (you cannot fly AR if you cannot see the deviation) — see the MEL article.

6. Layers — weather radar and terrain are mutually exclusive

The NAV modes can carry one overlay, but weather and terrain cannot coexist. Per FCOM DSC-31-45:

"The ND displays the EGPWS terrain picture, when the TERR ON ND switch is selected ON, and the ND is not in PLAN or ENG mode. The terrain picture replaces the weather radar image."

Terrain and weather are exclusive — TERR ON ND overrides weather. You cannot watch storms and terrain at once; TERR ON ND switches. One automatic logic: if a terrain alert (caution/warning) is generated with TERR ON ND not selected, the system auto-displays terrain and lights the ON legend (CFIT outweighs weather). The terrain picture replaces the radar "TILT" indication with a blue "TERR" and scans from the centre outward. The weather-radar and EGPWS mechanisms, colours and alert levels are in ATA-34.

7. Waypoints, airports, holding patterns and MORA

The NAV/PLAN modes also draw a set of map elements, briefly: flight-plan waypoints = green diamonds (departure waypoint white), the WPT button adds database waypoints (magenta); airports in the plan use a star + white identifier (a starting-runway symbol if a runway is defined), the ARPT button adds other database airports (magenta star); holding patterns and procedure turns show only when part of the flight plan — at 160/320 NM a white arrow marks the turn direction, at shorter ranges the whole circuit is drawn. And one safety altitude worth listing. Per FCOM DSC-31-45:

"MINIMUM OFF ROUTE ALTITUDE (MORA): Provided that CSTR is selected and the selected range is 40 NM or above, the MORA FL is displayed. This Flight Level indicates the MORA permitted, within a circular area centered on the current aircraft position and enclosed by 40 NM of radius limit."

MORA is the safe off-route altitude within 40 NM around — but shown only with both "CSTR selected and range ≥ 40 NM", an obstacle reference you call up deliberately, not a permanent one. Their data sources and flight-plan logic are in ATA-22; the ND is only their canvas.

8. Centre messages and flags — a chain of map failure

The ND centre carries a set of messages, three of which form a progressive chain. Per FCOM DSC-31-45:

"MODE CHANGE Appears if there is a discrepancy between the selected mode on the EFIS control panel and the mode sent from the onside FMGEC, or while the DMC is preparing a new page. RANGE CHANGE Appears if there is a discrepancy between the range selected... and the range sent from the onside FMGEC. A MODE CHANGE message has priority over a RANGE CHANGE message. MAP NOT AVAIL Appears when one of the following occurs: - The MODE CHANGE or RANGE CHANGE message appears for more than 6 s, or - The FMGEC has failed, or - The FMGEC has delivered an invalid aircraft position."

The chain: turning mode/range, the DMC requests a new map and briefly shows MODE/RANGE CHANGE (a normal transition, a few seconds); but if it lasts more than 6 s, or the FMGEC fails / gives an invalid position, it escalates to MAP NOT AVAIL — the map cannot be drawn. So a brief MODE CHANGE is normal; MAP NOT AVAIL is the real problem. Flags follow the "flash 9 s then steady" rhythm of the PFD article. The full inventory:

ND centre messages / flags — quick reference (from FCOM DSC-31-45; mechanisms are in ATA-34/22, the ND being their display outlet):

(a) Centre map-status messages

(b) Navigation-receiver / course flags (flash 9 s then steady)

(c) Predictive windshear (PWS)

(TCAS messages are in ATA-34; two-side discrepancy messages are in the reconfiguration article.)

Self-test

[!note]- Q1. What are the six ND modes, which cannot overlay weather radar, and to what sector does ARC limit ROSE NAV? ROSE LS/VOR/NAV, ARC, PLAN, ENG standby. PLAN cannot overlay weather radar. ARC limits ROSE NAV to the forward 90° sector.

[!note]- Q2. The wind: which north for the figure, which for the arrow? The direction figure is relative to true north; the green arrow is relative to magnetic north.

[!note]- Q3. Give the five flight-plan line colours and the navaid four-colour code. Lines: active green, missed-approach blue, alternate dashed blue, secondary white, temporary dotted yellow. Navaids: green = current waypoint, white = TO, blue = tuned, magenta = optional.

[!note]- Q4. Can weather and terrain be shown together? What if a terrain alert occurs with TERR ON ND not selected? No — TERR ON ND replaces the weather image. On a terrain alert the system auto-displays terrain and lights the ON legend.

[!note]- Q5. Explain MODE CHANGE / RANGE CHANGE / MAP NOT AVAIL. Which is the real problem? Turning mode/range briefly shows MODE/RANGE CHANGE (normal). If it lasts > 6 s, or the FMGEC fails / gives an invalid position, it escalates to MAP NOT AVAIL — that is the real problem.

Key takeaways

References

• FCOM DSC-31-45 — six modes, wind/GS/TAS, flight-plan line colours, navaid shapes and colours, crosstrack error, weather/terrain layers, waypoints/airports/holding/MORA, centre messages and flags.
• AMM 31-65-00 — ND detailed logic and controls.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.